International Journal of Advanced Medical and Health Research

: 2021  |  Volume : 8  |  Issue : 1  |  Page : 12--15

Clinical profile of children with influenza A and B infections admitted to a tertiary care hospital in South India

Janani Arul1, Satheesh Ponnarmeni1, Sharmila Ferdinamarie2, Rahul Dhodapkar2, Peter Prasanth Kumar Kommu1,  
1 Department of Paediatrics, Pondicherry Institute of Medical Sciences, Puducherry, India
2 Department of Microbiology, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, India

Correspondence Address:
Satheesh Ponnarmeni
Department of Paediatrics, Pondicherry Institute of Medical Sciences, Puducherry


Background: The influenza pandemics have caused serious morbidity and mortality around the world. Only a few studies have described the clinical profile of both influenza A and B infections among children and its seasonal variations. Aims: To study the clinical profile of children with influenza (A and B) admitted to a tertiary care hospital in India over a period of 17 months. Methods: A retrospective case file review was done for all influenza-positive cases (by real time-polymerase chain reaction) admitted in the ward and pediatric intensive care unit of a tertiary care hospital from January 2018 to May 2019. Results: A total of 164 admitted children were screened for influenza, of which 41 children (25%) were positive. Seasonal variation showed highest peak in the month of October with 17 positive cases (41%). Influenza B was observed during the first half of the year 2018 followed by an increase in influenza A infection in the last 6 months. The common presenting symptoms were cough (16, 39%) and respiratory distress (21, 51%). Out of 41, 18 children (44%) required respiratory support, but only 2 (5%) required mechanical ventilation. Hyponatremia was present at admission in 13 (61%) of 21 (51%) tested samples. The median length of hospital stay in the admission hyponatremia group was 7 days (interquartile range [IQR] 4, 15) as compared to the overall median length of stay of 4 days (IQR 3, 7). Conclusions: Our study showed a predominance of influenza B in the first half of the year and influenza A infection during the second half. A similar pattern was also seen in the first half of the subsequent year. Further studies are required to understand the impact of hyponatremia in these patients.

How to cite this article:
Arul J, Ponnarmeni S, Ferdinamarie S, Dhodapkar R, Kommu PP. Clinical profile of children with influenza A and B infections admitted to a tertiary care hospital in South India.Int J Adv Med Health Res 2021;8:12-15

How to cite this URL:
Arul J, Ponnarmeni S, Ferdinamarie S, Dhodapkar R, Kommu PP. Clinical profile of children with influenza A and B infections admitted to a tertiary care hospital in South India. Int J Adv Med Health Res [serial online] 2021 [cited 2021 Nov 29 ];8:12-15
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Full Text


The annual influenza epidemics are a major cause of burden of illness in children. Although a great majority of them are treated as outpatients, severe forms require hospitalisation.[1] The flu epidemics occur due to antigenic shifts, that expose the population to novel strains. The novel H1N1 strain of Influenza A (1918–1919) re-emerged in 2009 through the combined reassortment of swine, human, avian, and Eurasian genetic elements.[2] The global outbreak of swine flu (H1N1) influenza began in the border of Mexico and United States of America in April 2009. India witnessed the first swine flu epidemic in June 2009 in Pune, where nearly 40% of those affected were children <14 years of age.[3]

Influenza B came later into the picture around the mid-1940s when 2 antigenically different influenza B lineages (subtypes: B/Victoria and B/Yamagata), were identified. Even though, in the recent decades research was mainly focused on influenza A due to its pandemic potential and higher virulence, recent studies have shown the impact of influenza B infection as well.[4] Hence, in our study, we present the clinical profile of real time-polymerase chain reaction (RT-PCR) confirmed influenza A and B infections in children admitted in our hospital over a period of 17 months.


A hospital-based retrospective, descriptive study was conducted at a tertiary care medical college hospital located in Puducherry, India. The study protocol was approved by the Institutional Research Committee and ethics committee. All children who presented with Influenza-like illness (ILI) were screened and RT-PCR was done. Positive children were recruited into the study. The study population included the RT-PCR confirmed patients presenting to our in-patient department and pediatric intensive care unit (PICU) with respiratory distress, stridor, chest pain, hypotension, cyanosis, irritability, and poor feeding from January 2018 to May 2019. Only category C children according to guidelines of the National institute of Health and Family Welfare, India (NIHFW) were recruited into the study.[5] A total of 164 suspected cases (according to NIHFW) admitted in the ward and PICU were tested by sending nasal swabs for RT-PCR to the regional accredited virology lab at Jawaharlal Institute of Postgraduate Medical Educations and Research (JIPMER), Puducherry.

Demographic details including age, gender, residence, perinatal, and immunization history were obtained from the case records. The clinical details included presenting symptoms and signs, admission diagnosis, duration of symptoms prior to admission, and underlying medical conditions. The severity was assessed based on length of hospital stay, need of PICU admission, and need of oxygen support and mechanical ventilation. Nasal swabs were collected by doctors for all children with suspected ILI as per standard guidelines and sent to JIPMER virology lab for testing in a viral transport medium under strict cold chain measures as per the national guidelines.[5] RT-PCR was performed on all nasal swab samples for both influenza A and B viruses.

Along with the nasal swab, blood gas, complete blood count, serum sodium concentration, liver profile, and chest radiograph (CXR) were done for all patients in PICU and some patients in the ward as per unit policy. All the children admitted with pneumonia-like infection were started on antibiotics as per unit policy and tested for bacterial infection. Antibiotic was stopped if the blood culture was sterile.

The influenza-positive cases were treated with oseltamivir for a period of 5 days and chemoprophylaxis for close contacts for a period of 10 days from the last exposure as per the guidelines of the Ministry of Health and Family Welfare, India.[5] Quantitative data were presented as mean ± standard deviation or median and interquartile range (IQR), as appropriate. Normality of data was checked by the measures of Kolmogorov–Smirnov tests of normality. Categorical variables were expressed as numbers and percentages. Data were analyzed using the Microsoft excel (version 2014) and R Foundation for Statistical Computing (version 2020), Vienna, Austria.


A total of 164 children with ILI based on International Classification of Diseases codes) admitted in the ward and PICU between the months of January 2018 and May 2019 were tested for influenza by nasopharyngeal swab RT-PCR. The clinical profile of 41 (25%) children with RT-PCR confirmed influenza A and B infections with category C involvement were analysed. The seasonal time distribution of suspected and positive influenza cases admitted in the hospital during the study period is shown in [Figure 1]. The distribution shows a steep rise in the number of cases during the month of October 2018. Interestingly, influenza B accounted for 83% of all influenza cases (10 out of 12 cases) in the first 6 months of 2018 (January to June) followed by influenza A, adding to 83% of all positive cases (20 out of 24 cases) in the second half of 2018 (July to December). A similar predominance of influenza B virus infections in the first half of 2019 can also be appreciated in [Figure 1]. The two sub types of influenza A, namely H1N1 accounted for 46% (19/41) and H3N2 for 7.5% (3/41) of the total cases.{Figure 1}

The study population was categorized into four groups: Infants (<1 year), toddler (1–2 years), preschool (2–5 years), and middle childhood (5–14 years). Infants comprised the majority (48%) of the study population. Males (63.5%) were more frequently affected than females (36.5%). The predominant presenting examination finding was respiratory distress (21/41, 51%). The baseline clinical characteristics of the study population are shown in [Table 1]. Majority of the children (53%, 22/41) required direct PICU admission, the rest of the children were shifted to PICU when they developed respiratory distress. The positive cases were treated with enteral oseltamivir for 5 days (34/41, 85%) immediately after sending nasopharyngeal swabs, except for 7 children who required for more than 5 days. Of the entire study population, only two children (5%) had outside hospital stay and both did not receive antiviral treatment.{Table 1}

More than half of the positive cases (25/41, 62.5%) presented to the hospital after 5 days of onset of illness, hence all these children were already started on oral antibiotics from the referring hospital. These children (28/41, 70%) were treated with antibiotics for <7 days, till the blood culture was sterile as none of them had a bacterial infection (Blood culture was sterile in all patients). Relative lymphopenia (defined as <21% of total count) was observed in 10% (4/41) children (10). Mild elevation of aspartate aminotransferase and alanine aminotransferase was seen only in 5% of cases. C-reactive protein (CRP) was positive in 44% (18/41) of the children, with the median CRP being 22.5 mg/dL (IQR 14, 82). Out of 41 cases, 21 (51%) had serum sodium level measured at admission, out of which 13 of them (61%) had hyponatremia (serum sodium <135 mEq/L) and the lowest serum sodium value was 123 mEq/L. CXR showed varying degrees of lung infiltration suggestive of bronchopneumonia (41/20, 49%) followed by hyperinflation (9/41, 22%) and lobar pneumonia (7/41, 19%). One patient presented as acute laryngotracheobronchitis with CXR showing steeple sign.

Respiratory support was required for 18 children (43%), but only 2 children (5%) required invasive mechanical ventilation of which one patient had acute respiratory distress syndrome (2.5%), requiring mechanical ventilation for 7 days. The mean duration of oxygen therapy among nonventilated children was 48 ± 24 h. Multiorgan dysfunction syndrome with encephalitis, super refractory status epilepticus, and myocarditis was observed in one child with influenza A – subtype H3N2 (without any preexisting comorbidity). There was no mortality in the study group. The median length of hospital stay among the admitted children (with normal sodium at admission) was 4 days (IQR 3, 7). The median length of hospital stay among children with admission hyponatremia was 7 days (IQR 4, 15).


In our study, 25% of the children with ILI were positive for influenza A or B, which is similar to the studies by Mehta et al. and Samra et al. with 23% and 17% positivity respectively.[6],[7] Other south Indian studies have also quoted breathlessness and respiratory distress as the common admitting symptom and examination finding.[8],[9],[10] Blood investigations such as complete blood count were within normal range, except relative lymphopenia which was observed in 10% (4/41) of the cases. Some authors have found relative lymphopenia as a risk factor for longer duration of illness or requirement of mechanical ventilation.[10] Recent studies have highlighted elevated CRP in influenza patients, showing an association of CRP with influenza.[11],[12]

The CXR of 90% of children showed varying degrees of lung infiltrates to lobar involvement, similar to Chudasama et al. and Kumar et al. with 93% and 100%, respectively.[10],[13] The interesting finding was 7.5% of them had normal CXR and 22% had hyperinflation. Only 18 children (46%) required respiratory support, among them 2 (5%) required ventilator support.

The total influenza-positive cases peaked in the last 3 months of 2018 (October–December), with influenza B in the first 6 months and influenza A in the last 6 months of the year. Similar seasonal patterns have been observed in other studies.[14] Influenza A was higher with 54% of cases and influenza B accounted for (46%) the total influenza-positive cases. Oseltamivir was immediately started after sending nasopharyngeal swabs in all suspected cases. Finally, the variations in influenza A and B throughout the year are evident in our study, and we support the potential need for the use of the quadrivalent vaccine which has both (H3N2, H1N1) influenza A and (Victoria, Yamagata) influenza B.[15] In our study, serum sodium was measured at admission only in 51% of patients and 61% of the tested samples had hyponatremia, which is higher than the incidence of admission hyponatremia (ranging from 17% to 24%) in previous studies among children with bronchiolitis and lower respiratory tract infections.[16],[17] Children with hyponatremia had a longer duration of hospital stay as compared to their counter parts, which was a common finding in previous studies comparing outcome of patients with admission hyponatremia among children with lower respiratory tract infections.[16],[17],[18]

As this was a retrospective study, we had access only to the data available in the case files. Another limitation was the decision to send a nasopharyngeal swab was at the discretion of the practitioners, which may have led to missing some positive cases.


The influenza-positive cases peaked during the winter months from October to December. Influenza B accounted for 46% of all influenza cases and predominated in the first half of the year 2018 followed by a sharp peak of influenza A in the month of October when winter/monsoon starts in India. Respiratory support was required among 46% of children. Relative lymphopenia and elevated CRP have been observed in our severe influenza patients, hence, further studies are required to validate them as biomarkers for severe influenza.


We acknowledge the contributions of Dr. Lalitha Krishnan (PIMS, Puducherry) for inputs on modifying research methodology; Dr. Reba Kanungo (PIMS, Puducherry) for inputs on research methodology and for co-ordinating approval from JIPMER, Puducherry; Dr. Sheela Bazzroy and Dr. Shashikala N (PIMS, Puducherry) for helping with compiling the RT-PCR reports.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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